SAN FRANCISCO  Google showed off its nearly completed mobile software system to about 3,000 computer programmers Wednesday, hoping to cultivate more services and advertising for people on the go.

Although brief, the demonstration at the Internet search leader's annual developer conference in San Francisco represented the most extensive public look so far at "Android" — an open-source platform being designed for "smart" phones and other mobile devices that surf the Web. Android was first announced nearly seven months ago.

The bells and whistles unveiled Wednesday included: a way to unlock phones by drawing a specific shape on the touchscreen instead of entering a password; bookmarks for favorite websites on the device's home page; a "compass" tool that automatically roams with the phone while a user looks at photographic images of a city map; a magnifying tool to zoom in on Web content; and a mobile version of the video game "Pac Man."

The demonstration relied on touchscreen technology similar to Apple's iPhone, but Android can also be tailored to work with a tracking ball, said Andy Rubin, who is overseeing the project.

While acknowledging the work on Android is nearly done, Rubin deflected a question about how much longer consumers will have to wait for a phone powered by the new software. Sticking to the timetable Google has used throughout the project, Rubin said Android will hit the market some time during the final six months of this year.

Several handset makers, including Samsung Electronics., HTC and LG Electronics, are among the 34 partners that Google has recruited to help launch Android.

Google also hopes programmers will create a wide variety of products that will run on Android. That's one of the reasons the Mountain View-based company chose to flaunt the free software at the developers' conference.

By making it easier and more appealing for people to access the Internet on their cellphones, Google believes it eventually will make more money from the ads it shows next to search results and other Web content. The company also is starting to show more video advertising on its YouTube subsidiary, which already is a staple on the iPhone and received a special button in Wednesday's demonstration of Android.

Google is expected to generate more than $20 billion in advertising revenue this year, but most of that money will come from ads viewed on personal computers.

With about 3 billion mobile phones already on the market, some analysts believe Google could pull in nearly $5 billion annually from the mobile market within five years.

Google is also trying to boost its profits by selling more software services over Internet connections to businesses, universities and government agencies.

The company also wants to make it easier for outside developers to create applications on the Web. Even if those applications aren't on Google's website, the company figures it is bound to get more search requests — and more advertising opportunities — if people are doing more things online.

In April, Google handled nearly 62% of the search requests in the United States, according to comScore Inc.

Google's success so far is the primary reason Microsoft Corp., the world's largest software maker, spent several months trying to buy Yahoo before withdrawing its oral offer of $47.5 billion 3½ weeks ago when the two sides couldn't agree on a price.

Microsoft currently is discussing a smaller deal with Yahoo but hasn't ruled out the possibility of renewing its takeover attempt.

To help developers introduce more online products, Google last month began offering free computing power and storage on a limited basis under a service called "App Engine."

Google opened App Engine to all comers Wednesday and disclosed plans to begin offering extra capacity, for a fee, later this year. The service will remain free for up to 500 megabytes of storage and enough computing capacity to support 5 million monthly views of a site's Web pages.

Each additional gigabyte will cost 15 cents to 18 cents per month. Google estimated a user would pay $40 to $50 per month for enough capacity to support up to 10 million page views per month.

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